Electric discharge device and method of operation



Patented' June 13, 1944 snnc'rnrc DISCHARGE nnvrcn AND METHOD ororsna'rron Eugene Lemmers, signer to General tion of New York ElecCleveland Heights, Ohio, astric Company, a corpora- Application August1, 1941, Serial No. 405,060

'9 Claims.

This invention relates to electric discharge devices and theiroperation, and involves novelty in the control of electric discharges.One advantage that can be obtained through the invention is theelimination of troublesome accessories, in-

cluding starting and current-limiting means like ballasts,'thermalcut-out switches, etc. Another advantage is improvement of thevoltage-current characteristics of electric discharge devices, es-''pecially discharge devices containing gas or vapor, even to the extentof enabling such devices to start and operate with a positive overallvoltage-current characteristic, and without resort to specially highvoltage for starting. The invention is applicable to discharge devicesof suitable types already known, without necessity for any radicalmodification, and without need for elaborate or expensiveaccessories-though its range of useful capabilities can be considerablyincreased by the use of special features and arrangements that arereferred to hereinafter. The invention may be applied to dischargedevices producing useful'radiatlons for various purposes, such asgermicidal tubes or lamps, and lamps used industrially for irradiatingor treating many substances and products, and for fluorescent lighting.I have hereinafter explained the invention with particular reference toa device suitable for use as a fluorescent lamp.

Very generally, electric discharge through gases and vapors display anegative resistance or voltage-current characteristic. Suchcharacteristics are due to positive ions in the discharge atmos phere,which area necessary accompaniment and.

factor of the discharge, and which act to augment it in a cumulativemanner: i. e., ions once produced result in the production of more ions,which produce still more ions, etc., etc. Once the discharge is started,therefore, it automatically increases and "runs aware-unless the currentis limited by means of a ballast resistor, or the like, ,in series withthe discharge.

In the operation of one-way discharge devices on pulsating oralternating current, the discharge atmosphere is ionized or kept ionizedby the pemosphere, and so discharge recurs, intermittently, on eachvoltage impulse in the proper direction. If, on the other hand, bothelectrodes of a discharge device are emissive, the discharge takesplacein opposite directions alternately. In

' either case, it is the persistence of ionization in the dischargeatmosphere from one voltage impulse to the next that enables theionization and the dischaige to build up cumulatively from impulse toimpulse until (in the absence of extrinsic control over the current) thedischarge reaches run-away proportions, l I

In accordance with my invention, such persistence of ionizationisprevented; and if necessary, each period of discharge is additionallylimited in duration so that any real runaway in a single dischargeperiod is impossible.- For this purpose, 'an'intermittent discharge isinitiated and reinitiated at such periods in the series of voltageimpulses or of A. C. cycles that the duration of the discharge each timeis too short for the current to attain-an excessive value before thedischarge is terminated by fall of the discharge voltage; while theoutage interval from the resulting termination of the discharge to theinitiation of the next succeeding discharge permits substantialdeionization of the discharge atmosphere. If the duration of adischarge-voltage impulse or cycle is sufficiently brief, an outageinterval that assures adequate or substantial de-.

ionization before the next such impulse may afford all the controlnecessary. The explanation of why runaway does not occur in such casesriodically recurring pulses or waves 'of the discharge voltage and theconsequent emission of electrons from a charge device. During zero orreverse-voltage periods of the voltage cycle,'the emission of electronsand the discharge itself cease, and the discharge atmosphere starts todeionize: but the voltage impulses and the resulting emissions ofelectrons succeed one another before there is time for total decay ofionization in the discharge atcathode electrode of the dis-r seems to bethat during the part of each cycle when the discharge is going on, ionsare not formed fast enough, and the envelope walls have not time to trapenough of them to come to.

equilibrium; while by the next ignition, the ions have decayed away:hence each firing or discharge is essentially just like the onedirectly' before it. In other words, the intermittent main dischargesremain-isolated, as well as the auxiliary ionizing discharges thatinitiate them.

For GO-cycle A. C. current, it is found satisfactory in practice to fireor initiate one-way disharge on one peak of each cycle, which may beeither the positive or the negative voltage peak: e. g., the dischargemay be initiated somewhat before the voltage reaches its maximumpositive value or crest, or at any time thereafter while itspositive-value suffices for a'discharge across the discharge gap. Thismay be called quartercycle operation, since the discharge endures onlyabout one-fourth of each sine-wave period, while the remainingthree-quarters is available for deionization of thedischarge.'atmosphere, Apparently the deionization time is somethinglike $60 second. at any rate, such quarter-cycle opera-- tion does givea positive over-all characteristic to the discharge. For A. C. currentapproximating 25=cycle frequency, more or less, two-way dischargelikewiseshows a positivecharacteristic when suitably initiated on eachpeak (positive f and negativ'ei-of each cycle, since such half-' cycleoperation afiords substantially the same. length of time fordeionizationas does quartercycle operation on60-cycle A. C.

I have found that control of. ionization and discharge as aboveindlcatedcan be etlecied very simply and directly through the agency-oi anauxiliary ionization. of thedischarge atmosphere: i. e., theatmosphereis specially ionized during uch of themain voltage impulses or A. C.halfwaves that the main discharge thus initiated or ignited and theionization of the atmosphere that enables it to take place both die out.each time, before the next succeeding'ionization. Besides this choice ofperiods in the series of main Voltage impulses or half-waves which allowionization to decay, the particular points of the impulses or half-waveswhere ionization iseflected may be chosen according to the.duration and;wattage that are desired for the main discharge, as well as to allow itto die out, each time, too soon for the main discharge current tobecomeexcessive. An ionizing voltage or discharge for thesepurposesgranr similar to Figs. 1 and 3 showing a single discharge deviceand its connections, suitable for halt-cycle operation like the 0devices in Fig.3.

Figs. 6 and 7 are diagrams illustrating simplifled electrical supplysystems for discharge devices like that in Fig. 1 and Fig. 8 is asimilar diagram showing as somewhat different discharge device, as well;as a modified systemof electrical connections.

Figs. 9, 10, 11 and 12 are diagrams illustrating discharge devicessim'ilarto that of Fig. 1 with ancillary ionizing arrangementsandincluding electrical supply connections; Fig. 13 is a similar diagramshowing modifications in the discharge device, as well as in theelectrical system; and Fig. 14' is a similar diagram showing furthermodification of the device and of the electrical system. r

Fig. 1 illustrates the application of my invention to a well-knownsimple type of one-way electric discharge device that comprises avitreous tubular envelope ll having at one end anode disc l5 connected.to alead I'G-sealed through the end of the envelope, and having at itsother end .a cathode H which may be of filamentary thermion'ic type;(such as a coiled coil of tungsten may be provided in various ways, afew of which I have illustrated and explained hereinafter.

Such an auxiliary ionizing discharge may preferably Be A. C. Iorjthesake or simplicity oi -the power supply, if for no other reason. As thevoltage for this auxiliary discharge need on-its peaks only just aboveor a. little above the ionizing potential of the discharge atmosphere,and as the current required in it is butsmall, its

control as against running away presents np serious problem: the factthat it need only fire for an instant on the peaks of the auxiliaryvoltage cycle tends to give it an overall positive characteristic oiltsown; and any extrinsic control needed is aljiorded by the meansordinarily employed to deivoltage naturally .employed for the maindischarge. Control of the timing of the main discharge with respect tothe main voltage cycle may be effected either by adjusting the peakvalue of the auxiliary voltage, or by adjusting the f phase relationmetween the'mainkand auxiliary. voltage cycles. The frequencies of thesemain and auxiliary pulsating or A. C. voltage cycles will, in practice,bear a simple arithmetical relation to one another, if they are notactually' the same; and they will usually be approximately in phase,even when subject to slight adjustment of their phase relationiorpurposes 0! timing.

Various other features and advantages oimy invention will becomeapparent from thetollowing description of species and formsoffgmbodiment, and from the drawing. In the drawing, Fig. l is adiagrammatic illustration of a simple form of electric discharge d6?vice adaptable for the purposes 01 my invention,

,and of suitable electrical connections therefor;

Fig. 2 is a voltage diagram illustrating the operation of the systemshown in Fig. 1; Fig. 3 is a diagram similar to' Fig. 1 showing two suchd'is-' charge devices reversely' connected, rectifier V and strontiumoxides), and isshown co between leads l8, l8 sealed through the end ofwire activated with the usual mixture of arium ected the envelope.Provision fo'rpassing pulsating or A. 0. current through the cathodecoil I! may be made by connecting its leads l8, l8 across the secondaryof a transformer 20whose primary is connected by leads 2|, 2| across anysuitable auxiliary power source. p. The anode lead l6 and one of thecathode leads l8 are shown connected to a -main power circuit 22 fromany suitable pulsating' or A. C. power source P. The envelope, I4

a drop 23 inside the envelope l4, an an internal -rive the low auxiliaryvoltage from the higher may contain a low-pressure atmosphere of gas orvapor, or both, such as argon and mercury; or, preferably, the gas mayconsist of neon with a small admixture ot.argon--e. g., about 0.5% or5%. A surplus supply of mercury is indicated by coating of fluorescentmaterialor phosphor 25 on the envelope walls is also indicated. i

The pulsating or A. 0. main voltage from source l? should be suiiicient,at or near its peak value, to sustain a discharge between theelectrodesl5, ll, though not high enough to start one across so long a gap. Thepulsating or A. C. auxiliary voltage irom source 17 should not only besufllcient to heat the'cathode l'l toelectron-emissivejemperature, butalso highenough, at or near its peak value, to ionize the atmosphere inthe device, thus -producing an ionizing discharge along the oathode IIbetween its leads l8, I8 which results in or, in other-words. fires themain discharge. The

exact .time or 'stage ofits voltage cycle at which the main dischargethusfires may be varied'and controlled either by varyingthe phaserelation between the 1 main and auxiliary voltages, or by varying thrange and peak value of the auxiliary voltage wave, so as to change thepoint or stage in the auxiliary voltage cycle at which it reachesionizing value, or both. Variation of the auxiliary voltage is perhapsthe easier method; but variation'oi the phase relation affords -agreater range or control. The range of phase adjustment ordinarilyrequired is relatively small, so that the twovoltage cycles may alwaysbe approximately in phase withone another.

point of. main discharge ignition and of its duration in each voltagecycle may be helpi l not Adjustment of the ascna'ro one lead Itconnected to the main A. C. power cironly to insure against runaway ofthe discharge, but as a means of adjusting the lumen output rating of agiven fluorescent lamp. Furthermore, the luminous emciency may beincreased by reducing the wattage of the device, in this manner.

below that resulting from the earliest ignition consistent with apositive characteristic.

Assuming that the sources P and p both furnish 60-cycle A. 0., the maindischarge between electrodes l5 and I! will preferably be fired by theauxiliary discharge somewhat ahead of the crest of the main voltage peakof a half-cycle, and will persist till about the end of this half-cycle.This is indicated in Fig. 2 for the half-cycle I by the ordinate F1intersecting the main and auxiliary voltage curves V and v, and by theshaded area to the right of this ordinate under the curve V.

As her shown, the auxiliary and main voltage cycles are exactly inphase, and both discharges fire the instant the auxiliary voltagereaches-the ionizing potential of the'discharge atmosphere, ahead of thecrests of both voltage peaks. According to this diagram, in other words,the auxiliary voltage reaches and exceeds the ionizing potential E atthe crests of its own'peaks. Dying out when the main voltage falls tozero at the end of. this half-cycle, at the point 0, the main dischargeremains out during next halfcycle II because there'is no emissivecathode to support discharge in the reverse direction. During nearly orabout half of the ensuing half-cycle III, the main discharge is stillout, because the ionization from the previous discharges has decayed;but at the ordinate F2, somewhat ahead of the crest of this half-cycleIII, the auxiliary discharge will again ionize the atmospher in thedevice, and the main -discharge will again fire exactly as in the firstinstance-as indicated by the shaded area to the right of F2. Thisquarter cycle or quarter-wave operation continues ining anode 30 isconnected by a lead 3| to the definitely, as long as suitable pulsatingor A. C. voltages are supplied from p and P gested by the ordinate-F3.,r Fig. 3 shows a pair of one-way discharge devices such as hereinbeforedescribed reversely arranged and connected, rectifier fashion, so astogive approximate half-cycle operation as illustrated in Fig. 4. Fig, 4also diilers from Fig. 2. in. show-; ing the auxiliary voltage cycle asleading the main voltage cycle and firing on its own wave crests,instead of being in exact phase withth'e main voltage cycle and firingahead A of its own wave crests. According to Fig. 4, in other words, theauxiliary voltage only just reaches the ionizing potential Ed thedischarge atmosphere at the crests of its own peaks. In Figs. 3 and 4,various as is s scult 22, so that each of these electrodes I1 functionsaltemately'as cathode and as anode for the alternate main voltagehalf-waveaand also provides the auxiliary ioniiing discharge for thesehalf-waves. Accordingly, the same reference numerals are applied tovarious corresponding parts and features in Figs. 1, 3 and 5, as a meansof dispensing with repetitive description. So closely,.indeed, does thissingle Fig. 5 device correspond to the double Fig. 3 arrangement thatits operation on 25-cycle A. C. is essentially represented by the sameFig. 4 diagram.

It is convenient, of course, that the main and auxiliary voltage andcurrent sourcesPfp should be identical-4. e., that the auxiliary voltageshould be derived from the main voltage. Such a simplification is'illustra 6, where the cathode l7 main power circuit 22 in parallel with.the electrodes l5, IT by leads 21a, Zia and an interposed resistor 26,and in another form ln Fig. 7, where the primary of the transformer 20is connected by leads 2"), 2lb across the main power circuit 22 inparallel with the electrodes l5, H. A further variation is illustratedin Fig. 8, where the cathode I To is shown as of indirectly heated type,comprising. a heatin coil 21 connected between the leads, I80, I80 andsurrounded by an electron-emissive cylinder 28 coated with activatingmaterial 29. Here the auxiliary ionizing discharge takes place betweenthe activated cathode surface 29 and a separate auxiliary anode 30,while the coil 27 is only a heater-the voltage through which preferablyis not high enough to ionize; As here shown, the cathode cylinder andone of the heating coil leads l8care connected together and to one. endof the secondary of the transformer 200; the other lead me is connectedto the midpoint of this secondary; and the auxiliary ionizother end ofsaid secondary. Accordingly, the

. produce the auxiliary discharge.

parts :and features essentially correspondingto those in Figs. 1 and 2are marked with similar reference characters, thus dispensing withremately the-last l0% of petitive descriptions. The principal point tobe 6 observed is that one of the discharge devices .shown in Fig. 3fires on the positive half-cycles,

while the other fires on the negative half-cycles. Accordingly, thepowerfactor is very much better for this combination than for a singledevice op- 6 crating as illustrated in Figs. 1 and 2.

Half-cycle operation with its greatly improved power-factor can beobtained not only with two one-way discharge devices operatedvon -cyc1eA. C. as explained above in connection with Figs.

, The essentials for quarter-cycle operation on 60- cycle vA. C. asdescribed above are, of course, that the device should be able toconduct in but one direction, so as to fire only on alternatehalfcycles; that the main. discharge gapand voltage should be such thatthe device cannot fire on the firing half-cycles until ignited by theauxiliary ionizing discharge; and that this ignition be timed andlimited (in either of the ways ,hereinbefore indicated) to occur sometime during approxithe firing half-cycles. Even When the auxiliary andmain discharges are energized from a com 6, 7 and 8, the phase relationbetween the auxiliary and main voltages canbe adjusted to time theignition of the main discharge by various well-known means of displacingthe derived auxiliary voltage out of phase with the main voltage,

such as saturating transformers, chokes, or capacitors, for example.

A discharge device such as shown in Figs. 3, 6, and 7 may be built withan envelope tube M of 1 inch internal diameter 6 inches long;- with ananode plate I5 of sheet molybdenum inch in diameter; with a cathode l1consisting of. an-

ordinary l5-watt fluorescent lamp cathode; and

1 in having cathodes 11 at both ends, each with with a filling of argonat an absolutepressure of ted in one form in Fig, is connected acrossthe on source P,-as in Figs."

4 mm. of mercury, plus a mercury droplet 23 ample to assure a surplusduring operation. On Gil-cycle A. C.,' such a device operatessatisfactorily (without ballast) under a voltage of approximately 10volts (root mean square) across the cathode circuit Hand of 30 .volts'(root mean square) across the main power circuit 22, with a maindischarge current of approximately 0.4 ampere. The R. M. S. voltageshere stated correspond, of course, to substantially higher actualvoltages at the peaks of the A. C. sine waves, as represented in Figs. 2and 4. The main discharge current is very sensitive to small voltagechanges. either in the main power circuit 22, or in the auxiliarycircuit l8.

Besides the available voltage in the main power I circuit 22, thepracticable length of such a discharge device is limited by the distanceto which ionization from the glow discharge at the cathode I! willspread in the envelope tube It. For a 1- inch tube charged with argon,the length limit is about 8 inches to nearly 12 inches; but it increases as the diameter of the tube M is increased, and is also greatlyinfluenced by the composition of the atmosphere in the envelope H: e.g., ionization extends much further in an atmosphere of neon with asmall admixture of argon than in neon alone.

However, such limitations on tube length can in practice be overcome bymeans of ancillary ionizers at suitable intervals in the length of thetube, so that the zone of influence from one overlaps that of the nextone; and the tube length can be as great as permitted by the availablesupply' voltage. This is illustrated in Figs. 9-14, which show a few ofthe many possible arrangements and circuits.

Fig. 9 shows a one-way discharge device like that of Fig. 1 providedwith an intermediate auxiliary anode 35 located within the ionizingrange of the cathode I1, and close enough to the main anode Hi to bringthe latter within ionizing range of the discharge between the electrodes11 and 35. The electrode 35 is connected to the cathode side of the mainpower circuit 22 through the secondary of a leakage reactancetransformer 36 whose primary is connected across the circuit 22. Thetransformer 36 is so selected that the voltage between cathode I! andelectrode 35 is sufficient to produce discharge across this gap when theatmosphere is ionized by the discharge along cathode l1; whereupon theionization extends to the right-hand end of the tube and the dischargejumps to the main anode l5-thus short-circuiting and extinguishing orreducing to insignificant proportions the discharge between electrodesl1 and 35, owing to the resistance of the secondary of the transformer36 in series with the electrode gap "-35.

This Fig. 9 arrangement is peculiarly flexible because of thepracticallyunlimited choice of starting voltage across the gap |135 that isafforded through the selectionof the transformer 36: i. e., thisstarting volta'ge may, if desired, exceed the voltage of the source P bya wide margin. For example, a Fig. 9 tube of 1 inch internal diameter 54inches long may be operated without ballast on a voltage of 160 voltsacross the electrode gap I|-i5, using avoltage of 300 volts across theelectrode gap |'I-35 for starting.

The discharge device shown in Fig. 10 has an ancillary anode 35c locatedwithin the ionizing range of the auxiliary discharge at the cathode l1,and connected through a resistance 31 to the anode side of the mainpower circuit 22. Thus the full value of the main voltage from source Pis felt between the electrodes l1 and 35a until the gas is ionized bythe discharge at the cathode l1, whereupon the device breaks down firstto the ancillary anode 35c and then to the main anode I5, this dischargeshort-circuiting and thus extinguishing or reducing to insignificantproportions that between electrodes l1 and 35s, owing to the resistance31.

The discharge device shown in Fig. 11 involves a cumulativereduplication of the Fig. 10 arrangement: 1. e., the discharge betweenelectrodes 11 and 35e jumps first to another ancillary anode 35f andthen to the main anode l5, successively short-circuiting and reducing orextinguishing the discharges between electrodes l1 and 35e, 35f, owingto the resistances 31 and 31f.

The discharge device shown in Fig. 12 has two ancillary electrodes 359.and 38'connected through resistances 31g and 39 to the opposite sides ofthe main power circuit 22. The full value of th main voltage from sourceP is felt between electrodes 35g and 38 until ionization of theatmosphere by the discharge at the cathode ll. Thereupon dischargeoccurs across the electrodes 35g and 38, then jumps to the electrodes l1and I5, short-circuiting and reducing the discharge between 35g and 38,owing to resistances 31g and 39.

Fig. 13 shows a device which combines essential features of Figs. 6, 8and 10 in a simplified form. Its cathode l'lh is of indirectly heatedtype like that in Fig. 8, with its coil 21h (which merely heats, withouthaving any ionizing discharge along it) connected in a circuit 21hacross the main power circuit 22, and its cathode tube 28h grounded toone of .the coil leads lBh. It has an auxiliary ionizing anode 30hconnected to the anode side of the main power circuit 22 through a leadincluding a resistance 3lh such that the voltage of discharge across theelectrodes llh, 30h is just about sufiicient to ionize the dischargeatmosphere at or near the crest of its peak. 'Its ancilliary ionizinganode 35h and its connections may be essentially like the partsdesignated by the same reference numerals in Fig. 10. In order todispense with repetitive description, corresponding parts and featuresin Figs. 6, 8, 10 and 13 are marked with the same reference numerals-adistinctive letter being added where such distinction appears necessary.

The device shown in Fig. 14 resembles that of Fig. 13, but differs asregards the cathode of I11 and the auxiliary electrode 301: i. e.,- thecathode H7 is shown ofthe cold-starting activated coil type, like thatof an ordinary fluorescent lamp. andthe auxiliary anode 30a is locatedclose to it and connectedto the anode side of the circuit through aresistance 3 la'. Thus the full value of the main voltage from source Pis initially felt between the electrodes I17 and 3M, and suflices forcold-cathode initiation of discharge between them. Once this dischargeisstarted, its voltage is reduced to substantially the ionizingpotential of the atmosphere by the resistance 3M, and it continues as anauxiliary ionizing discharge like that in the Fig. 1 and other devices,igniting the main discharge at the proper points on the firinghalf-waves. If the desired length of the device requires, the ancillaryelectrode 357 with its resistance connection 317' may be provided,operating just likethe corresponding parts in Figs. 10. 11 and 13. Todispense with repetitive description, corresponding parts and featuresin Figs. 10, 11.13 and 14 are marked with the same refer- 2,351,270 encenumerals, distinctive letters being added where distinction seemsnecessary.- ,7 K

'What I claim as new and desire to secure by Letters Patent or theUnited States is:

1. A method of producing and controlling intermittent electric dischargethrough an ionizable atmosphere; which method comprises applying acrossa .main discharge gap between electrodes in said atmosphere amainpulsating voltage of peak value suflicient to sustain discharge to allowthe ionization accompanying each main discharge pulse ignited asaforesaid to die out be- 1 tore ignition or the next succeeding maindisacross said gap, but insuflflcient to initiate such discharge;intermittentlyfapplying across a gap between electrodes in saidatmosphere an ionizing potential suflicient to initiate a dischargethereacross, which ionizes said atmosphere andthus ignites a maindischarge pulse under said main pulsatingvoltage; and timing the.intermittent application of said ionizing potential to allow theionization accompanying each main discharge pulse ignited as aforesaidtodie out be- 'fore ignition of the next succeeding main discharge pulse.

2. A method of producing and controlling intermittent electric dischargethrough an ionizable atmosphere; which method comprises applying acrossa main discharge gap between electrodes in said atmosphere a'mainpulsating voltage of peak value-sufficient to sustain discharge acrosssaid gap, but insufficient to initiate such discharge; intermittentlyapplying across a substantially shorter gap' between electrodes in saidatmosphere an ionizing potential sufllclent' to charge pulse.

5. A method of "producing andcontrolling intermittent electric dischargethrough an ionizable atmosphere; which method comprises applying acrossa gap between main one-way discharge electrodes in said atmosphere a60-cycle voltage peak value sufllcient to sustain discharge across saidgap, but insuflicient to initiate such discharge; intermittentlyapplyingacross an auxiliary gap between electrodes in said atmosphere,

near the peaks of said 60-cycle voltage in the direction of dischargepermitted by said one-way discharge electrodes, an ionizing potentialsufficient to initiate a discharge across said auxiliary gap whichionizes said atmosphere and ,thus ignites a main discharge pulse betweensaid oneway discharge electrodes; and timing the intermittentapplicationoi said ionizing potential to allow-the ionizationaccompanyingeach main discharge pulse ignited aspaforesaidto die out abefore ignition oi the next succeeding main disinitiate a dischargeacross said shorter gap, which ionizes said atmosphere and thus ignitesa main discharge pulse under said main pulsating voltage; and timing theintermittentapplication of said ionizing potential to allow theionization accharge pulse.

6. A method of producing and controlling intermittent electric dischargethrough an ionizable atmosphere; which method comprises applying acrossa gap between main two-way discharge electrodes in said atmosphere avoltage of frequency approximating 25 cycles and of peak valuesuflicient to sustain discharge across said gap, but insufllcientto'initiate such discharge; intermittently applying across an auxiliarygap between electrodes in said atmosphere, near the peaks of saidvoltage in both directions, an ionizcompanying each main discharge pulseignited as ing potential sutficiimt to initiate a discharge across saidauxiliary gap which ionizes said atmosphere and thus ignites a maindischarge pulse between said main discharge electrodes; and

timing the lnterinittentv application of said ionizing potential toallow the ionization accompanying each main discharge pulse ignited asaforesaid to' die out before ignition of the next suc-- 'ceeding maindischarge pulse.

7'. In combination, anelectric discharge device comprising an envelopecontaining an ionizable atmosphere, and electrodes therein; means forapplying between electrodes aforesaid a main initiate a discharge acrosssaid shorter, gap, i

which ionizes safdatmosphere and thus ignites a main discharge pulseunder said main A. 0. voltage; and timing the cycles of said A.,C.ionizing potential to allow the ionization accompanying each maindischarge pulseignited as aforesaid to die out before ignition of thenext succeeding main discharge pulse.

4. A method of producing and controlling intermittent electric dischargethrough an ionizable atmosphere; which method comprises applying acrossa main'discharge gap between electrodes in. said atmosphere amain'pulsating voltage of peak-"value sumcient to sustain dischargeacross said gap, but insuflicient to initiate such dis.chargezr-intermittently applying across a substantia shorter gapbetween electrodes in said atmosphere a substantially lower potentialpulsating voltage approximately in phase with the pulsations of thefirst-mentioned voltage, and reaching the ionizing potential of theatmosphere only on its peaks, which thus ionize said atmosphere andignite main discharge pulses under said main pulsatingyoltage; andtiming the intermittent application of said ionizing potential pulsatingvoltage of' peak value sufficient to sustain discharge across their gap,but insuflicient toinitiate such discharge; and. means forintermittently applying between electrodes aforesaid an ionizingpotential suflicient to initiate a discharge thereacross, which ionizessaid atmosphere and thus ignites a main discharge pulse under said mainpulsating voltage, the intermittent application of ionizing potentialbeing timed to allow the ionization accompanying each main dischargepulse ignited as aforesaid --to die out before ignition of the 'nextsucceeding main discharge pulse. i 1

8. In combination, an electric discharge device comprising an envelopecontaining an ionizable atmosphere,-and electrodes therein afiording a'main discharge gap and a, substantially shorter auxiliary dischargegap; means for applying across-said main discharge gap am'ain pulsatingvoltage of peak value sufficient/to sustain discharge across said gap,but insuflicient to initiate such discharge; and means forintermittently applying across said auxiliary discharge gapan ionizingpotential sufiicient to initiate a discharge thereacross, which ionizessaid atmosphere and thus ignites a main discharge pulse across said maindischarge gap, the, intermittent application of ionizing potential beingtimed to allow the ionization accompanying each main discharge pulseignited as aforesaid to die out before ignition of the next succeedingmain'discharge pulse.

9. In combination, an electric discharge device comprising an envelopecontaining an ionizable atmosphere, and electrodes therein aifording aone-way main discharge gap and a substantially shorter auxiliarydischarge gap; means for applying across said one-way discharge gap amain A. C. voltage of peak value suiflcient to sustain discharge acrosssaid gap. but insuiiicient to initiate such discharge; and means forapplying gap which ionizes said atmosphere and thus il nites amain'discharge pulse across said one-way gap, the cycles of said A. C.ionizing potential being timed to allow the ionization accompanying:each main discharge pulse ignited as aforesaid: to die out beforeignition of the next succeeding;

main discharge pulse.

EUGENE LEW

